The present invention relates generally to resistive temperature detectors and more specifically to a method of making miniature wound wire resistive temperature detectors.
In the semiconductor industry, it is desirable for testing purposes to include a temperature detector within a die packaged cavity. Heretofore these temperature detectors have included semiconductor devices, for example, thermistors or diodes formed in a substrate or thin film resistors formed on the substrate. Process for forming these temperature detectors is compatible with other device forming techniques and thus is readily achieved while forming other devices in the integrated circuit.
In other environments, inexpensive temperature detectors have been used which include wrapping a resistive wire about a mandrel or form wherein the resistance of the wire changes with temperature. These devices are relatively inexpensive and may be produced without expensive equipment and time used to form temperature detectors on an integrated circuit. These wound resistors are relatively large and have not been made small enough to be used in a die cavity. The limitation of size is produced by the requirement to handle the mandrel or form during the winding operation. Special equipment to handle a form within the range of less than five hundredths of an inch diameter and lengths of less than one-tenth of an inch would require expensive and specially designed equipment. Similarly, in the past, the mandrel or form has generally been ceramic which requires molds or other special processing to produce each desired or specially designed form or mandrel. This special design for each individual case makes the wound wire temperature detector economically unfeasible to be produced small enough to be used in a die package cavity.